A flat bed printer is disclosed. The flat bed printer comprises: a bed on which a printed object is placed; an ink nozzle part arranged above the bed; and a gap adjustment unit for adjusting a gap between the ink nozzle part and the printed object by vertically moving the ink nozzle part. The gap adjustment unit comprises: multiple ball screw blocks installed in the ink nozzle part; multiple vertical screw shafts screw-coupled to the ball screw blocks and rotated to ascend or descend the ball screw blocks; and a power transmission structure for simultaneously rotating the multiple vertical screw shafts at the same speed using one motor.
